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Speaking hypothetically at Mr Cowan’s trial on Wednesday, Queensland Health forensic pathologist Dr Peter Ellis said compression of a child’s neck would not necessarily lead to instant death.

‘‘There’s so many different possibilities: whether bleeding has occurred, whether the airway is compromised, whether in fact the pressure has actually caused problems with the blood vessels and the nerves,’’ Dr Ellis said.

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‘‘I don’t think you can say damage to [the front of the neck] is the point of no return.’’

However, Dr Ellis said force applied in a ‘‘twisting or bending motion’’ to a child’s neck could cause death.

‘‘But ... I thought he was going to run ... and [I] grabbed him back in the house and choked him out.’’

Mr Cowan, 44, has pleaded not guilty to murder, indecent treatment of a child, and interfering with a corpse.

Seventeen bones, belonging to Daniel, were recovered from an abandoned sand mining site adjacent to the macadamia farm where the demountable house once stood.

Dr Ellis examined the bones and found they belonged to a ‘‘young growing human’’ in their early teens, the court heard.

The bones included the left and right upper arm bone, parts of a pelvis, segments of both lower leg bones and five vertebrae from the lower back.

‘‘The surface of the bones themselves were fairly dry. They were as you would expect bones that have been the ground for quite some time,’’ Dr Ellis said.

‘‘Some of them showed very small marks ... what one could describe as scratches ... from my observation they looked either more like the marks of an animal’s teeth, possibly even of the efforts of the excavating.’’

University of Adelaide researcher Dr Jeremy Austin examined a humerus (upper arm bone), which was recovered from the crime scene.

He said he searched for mitochondrial DNA testing in the bone sample because mitochondrial DNA - inherited from the mother only - survived longer in degraded samples.

‘‘The mitochondrial DNA profile from the bone sample was a 100 per cent matched to Denise Morcombe and to Denise’s other sons Dean and Bradley Morcombe.’’